SUMMARY Pre-biopsy evaluation of breast masses is a very critical step in selecting the right group to be biopsied. Current imaging methods, e.g., mammography and ultrasound (US), carry low specificity rates that lead to a great number of unnecessary biopsies. In the United States, the cost of potentially unwarranted biopsies is more than $3 billion annually and associated with significant trauma and anxiety for the patients due to this invasive procedure. Another area of uncertainty is assessing response to preoperative chemotherapy, where MRI has limitation due to high price and inaccessibility, the development of an alternative method with high accuracy is warranted. Our vision is to complement US with additional quantitative imaging information of microvascular morphology that is relevant to disease progression. We propose to develop a new type of imaging biomarkers, based on visualization and quantification of microvasculature morphology without using contrast agents, called ?Label- free Ultrasound Angio-Morphometry Analysis ((LUAMA)? to provide complementary diagnostic and prognostic information to conventional US. The goal of this research is to translate the new tool, LUAMA, as a clinical tool for assessment of breast masses. This technology is based on novel processing and quantification procedures to reveal and quantify microvasculature morphology using high frame rate ultrasound imaging. An advantage of this technique is that it does not require the use of contrast agents to produce high-resolution images of the microvasculature. We plan to address two aspects of breast cancer: identifying malignant masses and assessing preoperative chemotherapy response using 3D imaging system for a more accurate estimation of microvessel morphology. The project includes 2 specific aims: (1) Determine the diagnostic performance of LUAMA in a population of pre-biopsy patients with suspicious breast masses, correlate LUAMA results with pathology as the gold standard. (2) Assess and predict the response to preoperative chemotherapy in breast cancer patients using LUAMA and compare the results to MRI as control. This proposal is the result of collaboration among several experts in the field and benefits from the world-class clinical research and facilities at the Mayo Clinic. Successful completion of this research will open the door for a new technology for breast cancer patients in clinic. LUAMA is non-invasive, low cost, easy to use, and compatible with current US technology, which means that this technology can be readily translated to clinic and become available to a wide range of breast patients. Consequently, this research has potential to provide significant impact in breast cancer diagnosis and reducing unnecessary biopsies, as well as assessing response to preoperative chemotherapy.